The present disclosure relates to orthopaedic devices, and particularly to devices and apparatus for the reduction and fixation of fractures. The disclosed apparatus is useful, for instance, as a compression hip screw to treat femoral fractures occurring at the neck, head or trochanteric region of the femur.
The hip joint is the most heavily loaded and stressed joint of the human body. The joint is essentially a ball and socket joint, with the top of the femur fashioned into the ball that pivots within the cup-shaped acetabulum of the pelvis. The ball or head of the femur is connected to the shaft of the bone by the neck. The neck of the femur is particularly susceptible to fracture under certain loading conditions.
The treatment of such fractures is the same as for any bone—the separated portions must be held together while healing occurs. A variety of devices have been used to successfully treat femoral fractures, with perhaps the most common being the compression hip screw. In one approach, a lag screw extends through an aperture bored through the upper part of the femur and into the broken fragment to hold the broken fragment in proper position during healing. A plate secured to the outside of the shaft of the femur includes a barrel for supporting for the lag screw. A compression screw connects the lag screw to the barrel so that adjusting tension of the compression screw compresses or reduces the femoral fracture as the lag screw is drawn laterally toward the plate. One example of an apparatus of this type is disclosed in U.S. Pat. No. 5,041,116 to Wilson, the disclosure of which is incorporated herein by reference.
Intramedullary devices have also been used successfully to treat femoral fractures. In this approach, a rod or nail is inserted into the medullary canal of the shaft of the femur. Intramedullary rods are frequently used to treat fractures of the lower portions of the femoral shaft. Intramedullary rods are also used to support a lag screw and compression screw for treatment of fractures at the femoral head and neck. The intramedullary rod thus includes one or more transverse apertures to receive the lag screw and compression screw, if present. In some cases, two separate screws are engaged through the intramedullary rod and into the fractured portion of the bone to prevent rotation of the femoral head relative to the remainder of the femur. An example of a device of this type is disclosed in U.S. Pat. No. 5,562,666 to Brumfield, the disclosure of which is incorporated herein by reference.
One problem associated with many lag screw systems is excessive lateral collapse and/or back-out of the lag screw. In some cases, after the fixation device has been implanted the fracture will collapse, meaning the femoral head shifts laterally toward the femoral shaft. If this lateral shift is great enough, the lag screw can extend significantly from the femur, which can lead to patient discomfort and in more extreme cases disengagement of the lag screw from the fixation plate or intramedullary rod. Excessive lateral collapse may also lead to rotation of the fractured femoral head relative to the remainder of the bone, which can compromise proper healing. In these cases, revision surgery may be required.
There is a need for a fracture fixation and reduction apparatus that imposes a limit on lateral collapse of the fracture as well as on the lateral movement of the lag screw.